Such a device is previously known from the document WO 96/37922 (Allgon AB). The known device comprises a feed line structure integrated with a stationary array of antenna elements so as to enable adjustment of the direction of the beam radiated from the array. The feed line structure includes a feed conductor line pattern disposed on a fixed carrier plate at a distance from and in parallel to a fixed ground plate, and a movable dielectric plate located therebetween. The feed line pattern is elongated in the same direction as the movement direction of the dielectric plate. The propagation velocity of the signal components is reduced by the presence of the dielectric plate between the respective feed line and the ground plate. Accordingly, by displacing the dielectric plate in the longitudinal direction, the phase difference between the various signal components may be controlled.
In the previously known device, the feed line pattern is configured basically in meander-like loops with several loop portions extending back and forth in the longitudinal direction. Accordingly, the signal paths are relatively long, and the losses of microwave power being transferred in the device is relatively high. Moreover, because of the various meander-like loops extending in parallel to each other, the device is necessarily relatively wide in a transverse direction. Therefore, the overall dimensions of the device are relatively large.